The polygenetic Kahouanne Seamounts in the northern Lesser Antilles island arc: evidence for large-scale volcanic island subsidence

Carey, S. et al. (2020) The polygenetic Kahouanne Seamounts in the northern Lesser Antilles island arc: evidence for large-scale volcanic island subsidence. Marine Geology, 419, 106046. (doi: 10.1016/j.margeo.2019.106046)

Abstract

Remotely operated vehicle (ROV) explorations of the Kahouanne Seamounts, located 25 km SE of Montserrat in the northern Lesser Antilles island arc, have discovered the occurrence of honeycomb-scalloped erosional features on volcanic and limestone outcrops at depths of up to 600 m below sea level (mbsl). These features, combined with the flat-topped morphology of the seamounts, the occurrence of shallow-water carbonates (rhodoliths, benthic foraminifera), and the presence of oxidized, highly-vesicular volcanic fragments, suggest that the seamounts were once subaerial islands and have subsequently subsided to their present depth. The subsidence is likely to have been in response to a combination of 1) graben development southeast of the island of Montserrat where faulting and extension are driven by the accommodation of slip convergence associated with oblique subduction along the Lesser Antilles volcanic arc and 2) regional subsidence inferred from studies of nearby carbonate platforms. 40Ar/39Ar dating of basalt/andesite lavas from the central seamount indicates active volcanism around 5.4 Ma. Shallow-water carbonates recovered from an apparent wave-cut terrace at ~600 mbsl in the same area, were deposited approximately 3 Ma, based on Sr-isotope stratigraphy, indicating significant subsidence of the complex since that time. The total subsidence is in line with displacements in the Kahouanne valley graben and regional subsidence rates inferred from carbonate platform depths around the islands of Guadeloupe and Martinique, implying that intra-arc subsidence has been a significant process shaping the present bathymetry and topography of this island arc.

• Item Type: Articles
• Additional Information: Funding for research cruise NA037 of the E/V Nautilus was provided by the Office of Ocean Exploration of the National Oceanic and Atmospheric Administration (NOAA). Support for 40Ar/39Ar analysis came from grant 1114-1519 to S. Watt from the NERC Argon Isotope Facility. RSJS was supported by a Leverhulme Trust Emeritus Fellowship.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Barfod, Dr Dan
• Authors: Carey, S., Sparks, R.S.J., Tucker, M.E., Li, T., Robinson, L., Watt, S.F.L., Gee, M., Hastie, A., Barfod, D.N., Stinton, A., Leng, M., Raineault, N., and Ballard, R.D.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Marine Geology
• Publisher: Elsevier
• ISSN: 0025-3227
• ISSN (Online): 1872-6151
• Published Online: 20 October 2019